Twin Merc. 6.2 Mags with Bravo 3 - EMCT Temperature Overheat Fault - Port side Manifolds (Only)

[Ploring]

Well it’s good news so far. I really just needed to really understand how the Rinda works to clear faults (needed to clear the history) sensors are all reading now and no heater fault. No promises yet on the fuel fault but it’s clear and didn’t return upon startup

 

[Searay205]

The great thing about these MPI Cat engines is there is commonality with your automobile engine. Once you learn the different sensors as you are currently doing and their location the engine no longer looks like a big black box but pretty simple unless a gremlin keeps adding sensors at night, lol. One thing that took me awhile to comprehend is if the code indicates "fuel trim slow to respond" it probably isn't a bad sensor it probably, the fuel trim is slow to respond because an injector is leaking, or whatever. Also I test sensors now at the PCM wiring harness. Screw upside down on my head at the sensor. Truth be told the stuff is pretty straight forward with the service manual and again the knowledge is valid for you automobiles.

 

[Ploring]

Update- well took boat out today- first time since owning that the port engine “service engine soon” signal didn’t stay blinking after startup! This required a moment of applause…also no faults from the sensors.

True test came when I started to run up the engines.
2000 no problem
2500 no problem
3000 no problem
3200 guardian mode - port engine- fault EMCT temp too high. 212 degrees.
(Btw- I had cleaned all the carbon off this sensor before reinstalling.)
Starboard engine did not fault
I didn’t check EMCT temperatures until I was able to plug in the Rinda. Port engine Port fault manifold was 194 degrees, Starboard port manifold was 179 degrees.

I think the 3 year old pump is maybe the issue but my mechanic thinks it’s the manifold. He said “it’s probably not a flow thing it’s a restriction thing. New pumps last a long time and impeller should go 4 years”

Takeaway: boat runs great at trawler speeds!!

 

[alldodge]

New pumps last a long time and impeller should go 4 years”

IMO no, 3 tops and 2 years is better. If impeller is used year round, then 4 yrs is ok, otherwise 3 yrs

 

[Ploring]

It’s a Boston harbor boat for sure- he’s been doing this for 30 years though

 

[alldodge]

It’s a Boston harbor boat for sure- he’s been doing this for 30 years though

Recon ya got your answer then, if things change let us know

 

[Ploring]

Recon ya got your answer then, if things change let us know

Honestly I am torn. Ever replaced an impeller while floating? I understand I will need a plug to keep from sinking

 

[Searay205]

You need to ensure you have water flow. Volume. Your Rinda will tell you pressure what did it say? Where is your seawater pump, is this an Alpha 1 or Bravo 3? Alpha 1 in outdrive, Bravo 3 on engine. Engine has two water pumps one that pumps seawater to engine and one that circulates through engine. Circulation pumps rarely if ever go bad. Huge difference between the two seawater pumps is on pushes water the other sucks water and then pushes. Bravo 3 suck water, there is a disease call bravoites, over time salt water accumulates around the suction hose and collapses it reducing flow to nothing. quit blaming the manifolds if you so concerned remove and hydroblast. they will be clean.

Your overheat symptoms are identical to what I experienced on a Volvo Penta. Drove us fking nuts, new manifolds, new engine, new everything. I didn't know Volvo had the seawater pump on engine like a bravo 3 we were sucking air when we got on a plane in the outdrive where the water pickup was. Anything below 3K rpm we were 160F as soon as above 3K rpm we overheated. Again the issue with Bravo 3 is bravoitis? google it. You stick a boroscope ($30 on amazon) up the inlet water hose and see if it collapsed. Do a bucket test, verify flow.

 

[Searay205]

Just saw your title you have bravo 3. You need to verify unobstructed flow to your seawater pump. Any air leaks, restrictions screws you. Nice thing about Alpha you are pushing the whole way, nice thing about Bravo you don't have to take outdrive apart lol

I sure wouldn't loose any sleep with a new impeller, easy to do if you have room in front of engine, if possible take the suction hose free and blast with hose see if it all comes out outdrive. If it sprays back or acts restricted you have luggage. Easier than fking with manifolds

 

[Searay205]

You have tons of room. CHANGE THE IMPELLER AND RETEST. NO BRAINER. Pull suction hose and plug with bolt. Since other engine doesn't have problem and lived in same environment than hard to thing one has bravo tis and one doesn't. much more likely impeller worn etc

 

[Ploring]

Y’all are a world of information. So glad I joined the forum. Thanks! I think the pump/ bravo-itis is worth looking into

 

[Searay205]

Both manifolds running hot. Engine not? Other engine no issues lived in same environment. Sounds like flow issue. Enough flow to keep engine cool at low rpm's but as heat load increases due to load not enough water flow. Would really like to know engine temp when manifolds were hot. Oh wait you do, go to your history in Rinda and it tells you every reading and exactly when the alarm initiated. Bravo 3 impeller much larger than Alpha 1 impeller, you should have tons of flow.

That said my buddy sucked up an oyster shell and we chased that overheat for weaks, that how I know how to change out a B3 impeller. went out smacked into a bunch of waves between overheat alarms and all the sunned PING in exhaust and temps returned to normal, lol.

If you do blast manifold knock in the little freeze plugs, and pull back out. they are stainless and you can just reinstall. maybe put a little rtv around plug before tapping back in. That way you can blast everything. Again don't think that is your problem.

 

[Lou C]

Bravoitis involves the collar for the thru the transom hose necking down due to corrosion. You have to pull the drive to inspect. Merc & others make a repair kit but it can be tough to install depending on access.
With stern drives you should always troubleshoot overheating starting with a raw water flow test.
Each drive system has its issues that can cause overheating beyond worn impellers.
On my Cobra one problem I had to solve due to the boat being in salt water 4-6 months each year was marine growth on the water intake screen. These drives have a plastic screen inside the lower unit just like Evinrude & Johnson outboards had. What I would up doing was removing that screen entirely and making up a tool out of stiff wire that I can use to rod out the 4 large intake holes in the lower unit. I may have to do that if the boat isn’t getting used much, or the fouling is bad that particular year. Other than that the only other thing is replacing at least the exhaust elbows every 5/7 seasons.
One thing that trips up many is air getting into the raw water cooling via air leaks or combustion gas getting in via leaky head gaskets.

 

[alldodge]

Bravoits is checked by removing the intake hose fitting off the inside of the transom assembly, drive stays on

 

[Searay205]

Catalytic converters, bravoits, horrible access, my next boat will have an outboard. the inboard/sterndrive is dead.....

 

[Lou C]

Unless you find the right older boat that has no cats, big engine compartment etc.
A nice 26’ cruiser with a single big block and DP drive and large wide engine compartment.
The way they design sport boats with I/Os today is just awful, all about looks and stupid “features” like transom walk throughs that make the engine compartment smaller on the same side as the starter! What fools! Anything on the sides or rear of the engine will be a nightmare to get at.

 

[Ploring]

Sorry fell behind. Port port manifold was 212 at fault- didn’t see starboard port manifold until a bit later but it was 179. Both of these were triggering faults prior to the riser replacement. Looked up the pump history- seller gave me awesome receipts.

-New port seawater pump 2/2018 (bearing seal leaking)
-New impellers 2/2020 on both pumps
-New starboard seawater pump 7/2021 (bearing seal leaking- this was my mechanic)

So impellers are 1 and 2 years old.

 

[Searay205]

I fear Bravoits but with your model boat I would abandon the outdrive pickup and go with through haul fitting for water pick up.

 

[Ploring]

Bravoits is checked by removing the intake hose fitting off the inside of the transom assembly, drive stays on

Can this be done in the water- seems like the answer is no..

 

[alldodge]

Can this be done in the water- seems like the answer is no..

No, the boat would most likely flood

This is what it looks like